1. Field of the Invention
The present invention relates to a solution and method for cleaning integrated circuits, and more particularly to a solution and a method for cleaning a semiconductor or a liquid crystalline display substrate.
2. Discussion of Related Art
Cleaning processes typically play an important role in the manufacture of integrated circuits and semiconductor devices such as memory and liquid crystal device (LCD). The cleaning processes are crucial since integrated circuit substrates are easily contaminated during processing. Contaminants such as metal materials, oxide layers including native oxide layer, and damaged layers or even dust particles appear on substrates and affect the operation and reliability of the device. An effective cleaning process removes the contaminants, increasing manufacture yield rate.
A serial wet cleaning process is presently widely used. Examples of serial wet process are: APM (ammonia hydrogen peroxide mixture) process, SPM (sulfuric acid hydrogen peroxide mixture) process, and HPM (hydrochloric acid hydrogen peroxide mixture) process. The serial wet process can be effective in removing particles, organic contaminants, and metal contaminants, etc.
However, there are problems associated with serial wet processes. For example, the APM process can be effective in removing particles, but it is ineffective in removing metal contaminants. The HPM process can be effective in removing metal contaminants, but the HPM process is extremely corrosive and toxic as well as ineffective in removing particles. To obtain the desired cleaning effect, some manufactures apply these processes by mixing or transforming them appropriately.
As an example, according to a method of sequentially performing SPM, APM, and HPM processes, organic substances on the integrated circuit substrate (hereinafter substrate) are removed by the SPM process, while particles on the substrate are removed by the APM process. Then, the HPM process is performed to remove metal contaminants. However, this process in sequence is complex and manufacturing costs are high. Also there are environmental pollution dangers arising from continuous use of excessive cleaning solution and deionized water for a rinse process. Furthermore, since the SPM, APM, and HPM solution includes hydrogen peroxide (H2O2), which is a strong oxidizer, an oxide layer is formed chemically on a substrate after cleaning. In addition to the chemical oxide layer, a thin native oxide layer may be formed on a substrate when the substrate reacts with oxygen or water in the atmosphere during integrated circuit manufacturing process. If the thin native oxide is not removed efficiently, it may adversely affect the characteristics of an integrated circuit device. If the native oxide layer is formed on a contact surface, the contact resistance increases. Also, if the native oxide layer is formed before the growth of a gate oxide layer, the characteristics of the gate oxide layer is degraded.
Among methods of removing an oxide layer, one of the most widely-known process is wet cleaning using a hydrofluoric acid (HF) cleaning solution. The HF cleaning solution has an advantage in that the use of HF cleaning solution not only can maintain high selectivity between a substrate and an oxide layer but also forms a hydrogen passivation layer on the silicon substrate surface after cleaning an oxide layer.
However, there are disadvantages using the wet cleaning process with the HF cleaning solution. Since the process is difficult to perform in-situ and a long time wait is often required, step-by-step contamination control is difficult. Furthermore, during a subsequent process for dry cleaning of the substrate, the substrate is susceptible to contaminate. In addition, during the cleaning of a small and deep contact hole, it is difficult for the cleaning solution to flow into or flow out of the contact hole; therefore, the process cannot completely remove the oxide layer and cleaning residues in the small and the deep hole.
A method for removing contaminants from an integrated circuit substrate is provided. The method comprises first treating the substrate with a hydrogen peroxide cleaning solution containing a chelating agent. Subsequently, the substrate is treated with hydrogen gas and fluorine-containing gas, and the substrate is annealed.
According to an aspect of the invention, the hydrogen peroxide cleaning solution comprises ammonium, hydrogen peroxide, deionized water and a chelating agent and the temperature of the cleaning solution is about 40xc2x0 C. to about 80xc2x0 C.
According to a preferred embodiment of the invention, the chelating agent is present in an amount ranging from about 500 ppm to about 5,000 ppm based on the water content of the cleaning solution. The chelating agent includes one to three compounds selected from the group consisting of carboxylic acid compounds, phosphonic acid compounds, and hydroxyl aromatic compounds.
According to an aspect of the invention, the step of treating the substrate with hydrogen gas and fluorine-containing gas is preferably performed at a temperature of about xe2x88x9225xc2x0 C. to about 50xc2x0 C. and a pressure of about 0.01 torr to about 10 torr.
According to a preferred embodiment of the invention, the hydrogen gas and the fluorine-containing gas are supplied into a process chamber, the hydrogen gas in a plasma state and the fluorine-containing gas in a natural state. The fluorine-containing gas is a gas selected from the group consisting of nitrogen trifluoride (NF3), hexafluorosulphur (SF6), and trifluorochlorine (ClF3), and the amount of fluorine-containing gas supplied is about 0.1 vol % to 5,000 vol % with respect to the hydrogen gas.
According to an aspect of the invention, the step of annealing the substrate is performed at a temperature of about 100xc2x0 C. to about 500xc2x0 C. for about 20 seconds to about 600 seconds.
The method preferably further includes the step of rinsing with ozone water after treating the substrate with the cleaning solution. The cleaning solution treatment and the ozone water rinse are carried out within the same bath and the temperature of the ozone water is about 0xc2x0 C. to about 30xc2x0 C. The ozone water includes deionized water and ozone, and the content of ozone is about 1 ppm to 1000 ppm with respect to the deionized water.